Multi-layer information recording medium and recording apparatus for the same

Abstract

A stable rewritable multi-layer information recording medium capable of suppressing noises and a recording apparatus for the same. The multi-layer information recording medium is capable of recording/rewriting information, provided with a plurality of recording layers sequentially layered through spacer layers. Each recording layer is made of a material that changes reflectance upon irradiation of a beam of light, each recording layer is provided with alternately and adjacently aligned information rewritable regions and pre-pit regions where predetermined information has been written. Average reflectance of the rewritable regions is different from average reflectance of the pre-pits regions. In this construction, the pre-pit regions have recording marks that lessen a difference between the average reflectance of the rewritable regions and the average reflectance of the pre-pit regions. The recording apparatus for recording/rewriting information by irradiating a beam of light to a multi-layer information recording medium capable of recording/rewriting information, includes a circuit for generating a recording mark signal for recording a recording mark of a predetermined length in each of the pre-pit regions while the beam of light is irradiated on the pre-pit region.

What is claimed is:  
     
         1 . A multi-layer information recording medium capable of recording/rewriting information, comprising a plurality of recording layers sequentially layered through spacer layers, each recording layer being made of a material that changes reflectance upon irradiation of a beam of light and thereby being capable of recording information as a change in reflectance, 
 each of said plurality of recording layers being provided with alternately and adjacently aligned information rewritable regions and pre-pit regions where predetermined information has been written, average reflectance of said rewritable regions being different from average reflectance of said pre-pits regions,    wherein said pre-pit regions have recording marks that lessen a difference between the average reflectance of said rewritable regions and the average reflectance of said pre-pit regions.    
     
     
         2 . The multi-layer information recording medium according to  claim 1 , wherein each of said pre-pit regions is composed of a mirror portion and a portion provided with emboss pits.  
     
     
         3 . The multi-layer information recording medium according to  claim 2 , wherein said emboss pits carry address information.  
     
     
         4 . The multi-layer information recording medium according to  claim 1 , wherein each of said plurality of recording layers includes land tracks and groove tracks.  
     
     
         5 . The multi-layer information recording medium according to  claim 1 , wherein each of said recording layers includes a medium layer made of a phase change material.  
     
     
         6 . The multi-layer information recording medium according to  claim 1 , wherein said multi-layer information recording medium has a disc shape and said pre-pits regions are provided in a spokes-wise fashion from a center of the disc.  
     
     
         7 . The multi-layer information recording medium according to  claim 1 , wherein said recording medium has a disc shape and said pre-pit regions are provided periodically in a disc tangential direction.  
     
     
         8 . The multi-layer information recording medium according to  claim 2 , wherein a line of emboss pits in each of adjacent tracks are provided at a different position in a disc tangential direction.  
     
     
         9 . The multi-layer information recording medium according to  claim 1 , wherein each of the recording marks recorded in said pre-pits regions is a non-modulated continuous recording mark.  
     
     
         10 . A recording apparatus for recording/rewriting information by irradiating a beam of light to a multi-layer information recording medium capable of recording/rewriting information and comprising a plurality of recording layers sequentially layered through spacer layers, wherein each of said recording layers is made of a material that changes reflectance upon irradiation of a beam of light and thereby is capable of recording information as a change in reflectance, each of said plurality of recording layers is provided with alternately and adjacently aligned information rewritable regions and pre-pit regions where predetermined information has been written, and average reflectance of said rewritable regions is different from average reflectance of said pre-pits regions, 
 said recording apparatus including a circuit for generating a recording mark signal for recording a recording mark of a predetermined length in each of said pre-pit regions while the beam of light is irradiated on the pre-pit region.    
     
     
         11 . The recording apparatus according to  claim 10 , further comprising a circuit for detecting said rewritable regions and said pre-pit regions.  
     
     
         12 . The recording apparatus according to  claim 10 , further comprising a circuit for detecting a portion that makes the average reflectance of said pre-pit regions different from the average reflectance of said rewritable regions.  
     
     
         13 . The recording apparatus according to  claim 10 , further comprising: 
 a circuit for detecting the recording marks already recorded in said pre-pit regions; and    a circuit for, when no recorded recording marks are detected, controlling an optical pick-up to record the recording marks in said pre-pit regions, and when the recorded recording marks are detected, controlling the optical pick-up not to over-write the recording marks in said pre-pit regions.    
     
     
         14 . The recording apparatus according to  claim 10 , wherein a non-modulated continuous recording mark is recorded in a portion having a higher reflectance than the average reflectance of said pre-pit regions.